diff --git a/ChangeLog b/ChangeLog
index 5bb5e7de7a..2807f26887 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Sat Jul 30 11:21:55 2011  KOSAKI Motohiro  <kosaki.motohiro@gmail.com>
+
+	* vm_core.h (ALT_STACK_SIZE): use MINSIGSTKSZ*2 instead of SIGSTKSZ*2.
+
 Sat Jul 30 10:39:14 2011  KOSAKI Motohiro  <kosaki.motohiro@gmail.com>
 
 	* vm.c (th_init): preallocate alternative stack.
diff --git a/vm_core.h b/vm_core.h
index 5f4e5d47f1..21e7d866c5 100644
--- a/vm_core.h
+++ b/vm_core.h
@@ -383,8 +383,8 @@ struct rb_unblock_callback {
 
 struct rb_mutex_struct;
 
-#ifdef SIGSTKSZ
-#define ALT_STACK_SIZE (SIGSTKSZ*2)
+#ifdef MINSIGSTKSZ
+#define ALT_STACK_SIZE (MINSIGSTKSZ*2)
 #else
 #define ALT_STACK_SIZE (4*1024)
 #endif